Continuous desublimation apparatus



Dec. 23, 1969 E, B. TRICKEY.

CONTINUOUS DESUBLIMTION' r APPARATUS original Filed oct. 12. 1960 /NVENTOR E. Bruce Trckey by h/M/rnf/ //QMM ATTO/l NEYS Dec. 23, 1969 E. a. TRICKEY' l 3,485,589 CNTINUOUS DESUBLIMATIN APPARATUS original Filed oct. 12,1960 s sheets-sheet a F/G. 8 l D INVENTOR E. BRUCE TRICKEY BY Mm, M //Qm ATTORNEYS United States Patent O 3,485,589 CONTINUOUS DESUBLIMATION APPARATUS Elwood Bruce Trickey, Mobile, Ala., assignor to Gelgy Chemical Corporation, Ardsley, N.Y., a corporation of Delaware Continuation-impart of application Ser. No. 341,822, Jan. 2, 1964, which is a division of application Ser. No. 62,271, Oct. 12, 1960, now Patent No. 3,256,070. This application Oct. 19, 1966, Ser. No. 601,255

Int. Cl. B01d 7/00 U.S. Cl. 23--264 3 Claims ABSTRACT F THE DISCLOSURE An apparatus for desublimating cyanuric chloride and the like. A rotatable cooled initial desublimation charnber opens into a cooled -tinal desublimation chamber. The initial desublimation chamber has an inlet at one end thereof and a liner of corrosion resistant material on the inside thereof. A screen is provided between said initial desublimation chamber and said final desublimation chamber and a charge of particulate tumbling grinding media is positioned in said initial desublimation chamber. Said final desublimation chamber has an outlet therefrom for desublimate-d material and a vent for the escape of gases therefrom. A collecting means depends from said outlet, and a cooling medium supply system is positioned adjacent at least said rotatable initial desublimation chamber for tlowing a cooling medium over the outside of said initial desublimation chamber.

This application is a continuation-in-part of my application Se-r. No. 341,822 liled Ian. 2, 1964, now abandoned which in turn is a division of my application Ser. No. 62,271 filed Oct. 12, 1960, now U.S. Patent 3,256,070.

This invention relates to the preparation of solid, finely divided material in high purity by desublimation. In particular, the invention relates to the continuous preparation of solid, nely divided cyanuric chloride by desublimation. By desublimation is meant a change of state from a vapor to a solid, i.e. the reverse of what is normally thought of as sublimation.

It is an object of the invention to provide an apparatus to separate pure material, which is capable of sublimation and desublimation, said material being recovered in the highly desirable physical state of tine particles in high purity. Specically, it is an object of the invention to provide an apparatus for preparing cyanuric chloride in solid form by continuous desublimation. Other materials which are amenable to the method of continuous desublimation utilizing the apparatus are also within the scope of the invention, e.g. organic material, such as naphthalene, phthalic anhydride, salicylic acid, anthraquinone, etc., and inorganic material, such as the metal halides, aluminum chloride, etc. and also ammonium chloride, ammonium bromide, ammonium iodide, etc.

The `apparatus of the invention is particularly useful in the preparation of material which can be desublimed from the vapor state directly to the solid state. The usefulness of the invention will be further illustrated by the discussion and examples which follow.

In the hitherto known processes for the preparation in solid substantially pure form of desublimable material, e.g. cyanuric chloride, the product is produced in a vaporous form and has to be solidified by means of cooling, and the solid material then ground to the lineness required to further use. The vapor, c g. cyanuric chloride, solidies to an extremely hard almost glass-like mass which rmly adheres to all parts of the reacting chamber. It is therefore ditlicult to carry out the con- ICC densation of the vapor, e.g. cyanuric chloride, in the usual apparatus because of the danger of clogging the coolers, etc. In `order to collect the solid material for grinding, the walls of the desublimating chamber are mechanically scraped. While in practice the solid material seems to be collected continuously, the apparatus m-ust be shut down periodically for cleaning. In addition, the mate-rial thus collected must be ground to the proper particle size, and in practice this has been found to be rather diflicult to do satisfactorily. Moreover, the mechanical removal of the hard glass-like solid, e.g. cyanuric chloride, is especially diliicult Awhen the material itself and/or Vother materials with which it is mixed are very strong olfactory irritants as is true of cyanuric chloride. Further, in some cases, e.g. with cyanuric chloride, the product has a very low thermal conductivity and hence almost no heat exchange takes place at cooling surfaces coated with e.g. cyanuric chloride. The discharge of the heat of condensation set free in the solidification process is the more ditlicult, the greater the deposit of product, c g. cyanuric chloride. For the foregoing reasons an apparatus for carrying out a true continuous process for producing such substances, e.g. cyanuric chloride, in -nely divided form has been impractical or impossible.

It has now surprisingly been found that many inorganic and organic materials which desublime can be prepared in granulated form by the apparatus according to the invention which carries out a continuous process. For example, according to the invention, cyanuric chloride is not only continuously precipitated in the apparatus according to the invention, but it is also recovered in a finely divided iiuffy state without any further mechanical comminution. It is preferred to practice the invention in such a way that the conversion of vapor to solid occurs at a rate whereby no strongly adhering coatings of solid, e.g. cyanuric chloride, are formed within the cooled rotating chamber of the apparatus wherein the grinding media are placed.

Preferred embodiments of the apparatus of the present invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of one embodiment of an apparatus according to the present invention in which a continuous process can be carried out;

FIG. 2 is a sectional elevation view of the apparatus of FIG. 1;

FIG. 3 is a cross sectional View taken along line 3--3 of FIG. 2;

FIG. 4 is a sectional elevation view, on an enlarged scale, of a detail of the apparatus of FIG. 2;

. FIG. 5 is a sectional elevation view, on an enlarged scale, of a detail of the apparatus of FIG. 2;

FIG. 6 is a cross sectional View, similar to that of FIG. 3, of a modification of the apparatus of FIG. 2;

FIG. 7 is a perspective view of another embodiment of the apparatus according to the invention; and

FIG. 8 is a sectional elevation view of the apparatus of FIG. 7.

The embodiment of the apparatus shown in FIGS. 1 6 comprises a base frame 10 of channel beams, on one end of which is secured an upright 11. Fixed on the upper end of the upright is a hollow axle 12 which extends horizontally. Positioned around the axle and rotatably mounted thereon is a bearing and seal housing 13 having a bearing and a seal therein which bear on the outside of the hollow axle 12. Secured on the bearing and seal housing 13 is a sprocket wheel 14 which is driven by a roller chain 15, which is in turn driven, through reduction pulleys and belts 16, from a motor (not shown).

Mounted on the bearing and seal housing 13 is the end Wall 18a of a rotatable cooled initial desublimation chamber in the form of a drum 18 which is shown as cylindrical with its axis horizontal. At the end of the drum 18 opposite the end which is secured to the bearing and seal housing 13 the drum 18 has a bearing ring 19 therearound. The end of the drum within the bearing ring 19 is open and has a screen 20 thereac-ross, which is secured to the end of the drum 18 by a retaining ring 20a and which delineates the end of the initial desublimation chamber.

Surrounding the open end of the drum 18 is a cooled {nal sublimation chamber in the form of a hood 21 into which the drum opens, and a felt seal 22 covers the joint between the end of the drum and the hood. The hood has a top 23 thereon with a vent 24 therein, which can open into a stack or other gas disposal system. The hood opens downwardly and has a discharge funnel 25 attached to the bottom thereof which empties into a collecting container 26. A circular opening is provided in the side of the hood 22 opposite the side into which the drum opens, and a cover plate 22a covers the opening.

Mounted on the side of the hood 21 toward the drum 18 is a bearing mount 27, on which are mounted two roller bearings 28 on which the bearing ring 19 rolls. The bearings 28 are at a level such that the end of the drum 18 at the hood 21 is supported with the axis of the drum 18 in a horizontal position.

Within the drum are a plurality of agitating rods 30, which are spaced inwardly to the liner a distance which is from j/-1/3 the diameter of the drum. These rods may be secured at one end to the end wall 18a of the drum and at the other end to supports (not shown) which extend inwardly from the liner.

Positioned above the apparatus is a system of pipes 31 for spraying a cooling medium over the outside of the drum. These pipes include a header 32 and individually valved depending pipes 33 having spray heads 34 on the ends thereof. The cooling medium flows down over the outside of the drum 18 and falls into a collecting means (not shown) on or below the frame 10. A flange 35 is provided adjacent the bearing ring 19 to prevent cooling medium from flowing along the drurn past the point' at which the flange is positioned, and a further flange is pro- 'vided at the end of the drum which may be formed by extending the end wall 18a as at 1811.

The details of the rotatable mounting of the drum on the hollow axle 12 are shown in FIG. 4. The bearing and sealing housing 13 is welded to the end wall 18a of the drum, and has an inwardly extending seal retaining ange 36 on the inner end thereof. Against the ange 36 is positioned a seal retaining ring 37. A seal 38 is held against the seal retaining ring 37 by an intermediate ring 39, which in turn is held in place by the action of a sealed bearing 40 bearing against it. The sealed bearing 40' is :mounted on the hollow axle 12 and is held in position by a bearing retaining ring 41, xed to the hollow tube 12 by a set screw`42, the bearing ring holding the bearing 40 against the shoulder 43 on the hollow bearing tube 12. A gland 44 bears against the opposite side of the bearing 40 from the intermediate ring 39, the gland having the sprocket Wheel 14 secured thereto. The gland also has a ange 45 thereon having a plurailty of bolts 46 extending therethrough and threaded into the end wall 18 of the drum. Nuts 46a on the bolts serve to draw the gland toward the drum, thus urging the bearing 40, the hollow axle 12, the intermediate ring 39, the seal 38 and the seal retaining ring 37 against the seal retaining flange 36.

The details of the bearing mounts 27 andthe roller bearings 28 thereon are shown in FIG. 5. An upright bearing support 47 is welded to the frame of the bearing mount, and a bearing axle y48 is bolted to the bearing support 47. A ball bearing 49 is mounted on the bearingv axle 48, one race 49a of -which is fixed to the axle, and

.4 the other race 49b of which supports the bearing ring 19 on the drum.

The bearing ring 19, as seen in FIG. 5, can be formed of a separate cylindrical ring member having a radical dimension greater than the wall thickness of the drum 18. The ring can be welded to the end of the drum as at 50. The ring has a sealing ange recess 51 therein at the free end thereof, into which ts a sealing flange 52 which projects toward the drum from the discharge hood 21. The felt seal 22 overlaps the joint between the sealing ange and the bearing ring 19.

In the modification shown in FIG. 6, the agitating rods 30 are augmented by lifting bars 53, which are mounted around the inside of the drum wall and which project into the drum toward the center thereof. These serve to left the grinding meda which collect in the bottom of the drum as it rotates and lift them at least part way around the drum.

Further, the interior of the drum 18 is lined with a liner 29 of a material which is resistant to corrosion and which promotes the grinding, as will be discussed hereinafter.

Particulate tumbling grinding media 54 are provided in the drum for purposes to be discussed hereinafter with respect to their action in the process as carried out by the apparatus of the present invention. The material of which the grinding media are made will also be set forth hereinafter.

In the continuous process as carried out in the apparatus of the invention, a flow of vapor, e.g. cyanuric chloride, plus lminor amounts of gases such as chlorine and cyanogen chloride carried along with the vapor from the proc# ess of making the cyanuric chloride, is continuously passed into the end of the rotating drum through the hollow axle 12, while the exterior is cooled with water from the pipe System 31. The individual pieces of the grinding media 54 will, as the drum rotates tumble over and keep striking one another and also strike the surface of the liner 29 of the drum. Most of the Vapor solidies within the drum, the surfaces where deposits can occur being continuously kept clean by the action of the grinding media 54 which are more fully described hereinbelow, striking each other and the drum liner. The 4iinely divided solid material, e.g. cyanuric chloride, which is produced in the drum is continuously discharged into the discharge hood 22 at the end of the rotating drum opposite to the hollow axle, and the solid material falls down the funnel 25 into the collecting container 26.

There is also passed into the hood 21 a mixture of the gases carried along with the vapor introduced into the drum 18, which mixture is just saturated with cyanuric chloride Vapor. yIt is highly desirable to recover this desublimable material for economic reasons, and it may even be said to be essential to recover it for safety reasons, the cyanuric chloride gas being very toxic and corrosive. The cooled final desublimation chamber or hood 21 is provided for this purpose. It is air cooled by the ambient atmosphere suiiciently to cause the cyanuric chloride vapor in the mixture of gases to desublimate in finely divided form right in said mixture of gases rather than on any surfaces in said yfinal desublimation chamber, this desublimation being given the name snowing out. The thus finely divided desublimed material falls into the discharge funnel along with the comminuted material from the drum 18, and the mixture of gases which remains passes out the vent 24 into a stack or recovery system substantially free of cyanuric chloride.

The embodiment of FIGS. 7 and 8 also comprises a base frame of channel beams, on one end of which is secured an upright 111. Fixed on the upper end of the upright is a hollow axle 112 which extends horizontally.v

Positioned around the axle and rotatably mounted thereon is a bearing and seal housing 113 having a bearing and a seal therein which bear on the outside of the hollow axle 112. Secured on the bearing and seal housing 113 is a sprocket wheel 114 which is driven by a roller chain 115, which in turn is driven, through reduction pulleys and belts from a motor (not shown).

Mounted on the bearing and `sealing housing 113 is the end Wall 118a of a cooled initial desublimation chamber in the form of one portion 118 of a drum which is shown as cylindrical with the axis thereof horizontal. About midway along the length of the drum at the end of the one drum portion 118 is a screen 120 which extends across the interior of the drum and which marks the end of the initial desublimation chamber. The Screen 120 can be secured to the inside surface of the wall of the drum, for example by a retaining ring 12Go.

Extending from the said one portion 118 of the drum is the other portion 121 of the ldrum terminating in an end wall 118b which delineates the end of the final desublimation chamber constituted by the said other portion 121 of the drum. Mounted on the outside of theend wall 118b is a bearing and seal housing 113m having a bearing and seal therein which bear on the outside `of a second hollow axle 122 which extends through the bearing and seal into the interior ofthe drum portion 121. The portion of the second hollow axle 122 outside the drum is mounted on a second upright 111a which is secured on the base frame 110.

Extending into the said other portion 121 of the drum from the inner end of the hollow axle 122 is an open topped trough 123 which has a screw c'onveyor 124 therein which extends through the hollow axle 122 and out the other end thereof, and the shaft 125 of which is driven by a pulley 126, preferably from the motor. Mounted on the inside surface of the drum wall at the end of the said other portion 121 of the drum are lifting members 127 which project inwardly from the wall into the drum.

Around the outer end of the hollow axle 122 is a hood `128 having a downwardly extending collection chute 129 and an upwardly extending stack 130. The chute 129 is adapted to extend into a drum D for the collection of the comminuted cyanuric chloride, and the stack 130 extends either to a venting system or t-o a collection system for the waste gases.

Positioned above the apparatus is a piping system 131 for spraying a cooling medium over the outside of the drum. This system can be the same as the system for the embodiment of FIGS. 1-7.

Particulate tumbling grinding media 1'54 are provided in the said one portion 118 of the drum for the cleaning and grinding action during the initial desublimation of the cyanuric chloride in the said one portion of the drum. They are retained in said one portion 118 of the drum by the screen 120.

In the continuous process as carried out in this embodiment of the apparatus of the invention, a flow of vapor, e.g. cy-anuric chloride, plus minor amounts of gases such as chlorine and cyanogen chloride carried along in the vapor from the process of making the cyanuric chloride, is continuously passed into the one end of the rotating drum through the hollow axle 112, while the exterior of the drum is cooled with water from the pipe system 131. The individual pieces of the grinding media 15,4 will, as the drum rotates, tumble over and keep striking one another and also strike the inner surface of the initial desublimation chamber portion 11-8 of the drum. Most of the vapor solidifies within this initial desublimation chamber portion 118, the surfaces Where deposits can occur being continuously kept clean by the action of the grinding media 154, which are more fully described hereinafter, striking each other and the inside of the drum wall. The finely divided solid material, e.g. cyanuric chloride, which is produced in the initial `desublimation chamber portion of the drum is continuously discharged into the final desublimation chamber portion 121 of the drum in a finely comminuted condition.

There is also passed into the final desublimation chamber portion a mixture of the gases carried along with the vapor introduced into the drum, which mixture is just saturated with cyanuric chloride vapor. It is highly desirable to recover this desublimable material for economic reasons, and it may even be said to be essential to recover it for safety reasons, the cyanuric chloride gas being very toxic and corrosive. The cooled final desublimation chamber portion 121 of the drum is provided for this purpose. The cooling medium from the pipe system 131 cools the walls of the portion 121 of 4the drum suiiiciently to cause the cyanuric chloride vapor in the mixture of gases to desublimate in finely divided form right in said mixture of gases rather than on any surfaces in said final desublimation chamber portion of the drum, this desublimation being given the name snowing out. The thus finely divided desublimed material falls into the comminuted material from the initial desublimation chamber portion 121 of the drum and is picked up by the lifting members 127 and directed into the open trough 123, where the screw conveyor V124 conveys it along the hollow axle 122 and into the hood 128. It then falls into the chute 129 and a drum D. The remaining gases pass into the stack 130 from which they are vented or collected.

The grinding media not only keep the interior surface of the drum as well as the surfaces of the particles of the grinding media clean but also further grind the product, e.g. cyanuric chloride. Thus, almost all of the product, e.g. cyanuric chloride, is in the form of particles less than 40 micron. Further, the grinding media are self-cleaning.

In the process of the invention a product having a very fine particle size is obtained. The size of the particles produced ranges from about 1 micron to about 200 microns. This fine particle size represents one of the distinct advantages of the present invention, since not only high purity but a finely divided physical state is a desideratum of the invention. The particle.` size is closely related to the size and quantity of the grinding media, to the charge rate of the material to be purified and to the speed of rotation of the mill wherein desumbilmation and grinding occur. The temperature of sublimation at normal atmospheric pressure for material within the scope of the invention, e.g. cyanuric chloride, ranges from about 40 C. to about 500 C. The cooling of the drum should be so controlled as to allow almost instantaneous desublimation. Also the charge rate of the vapor to be desublimed must be so controlled as to avoid buildup of a glass like layer of solid on the interior lining 29 of the drum.

The grinding media 54 are any suiatble shape such as, e.g. spheres, cubes, cylinders and irregular shapes. No shape is contemplated the effective length of which falls without the range from about one-eight inch to about four inches. The effective length is understood to be the line having the shortest length which might be drawn through the center of the solid shape such as, e.g. the height or diameter of a cylinder, the edge dimension of a cube or the diameter of a sphere, etc. The effective length is related closely to the specific gravity of the grinding medium. Lighter materials, of course, may have a larger effective length. The speci-fic gravity of useful materials for grinding ranges from about 2 to about 11.3. It is preferable, however, to use a heavy material in quantity just sufiicient to keep the walls of the drum clean and produce a product of suitable particle size. Preferred materials include nickel, iron, steel, quartz, flint pebbles and porcelain. High density ceramic materials, e.g. Burundum a synthetic sapphire substance in bond, composed of specially prepared fine grain crystals of aluminum oxide held together by a non-metallic vitreous bond (US. Stoneware) are useful.

The so-called Ni-hard (International Nickel C0.) material is also useful: The composition of Ni-hard is iron, percent; nickel 4.5 percent; slicon, 0.6 percent; carbon, 3.4 percent and chromium 1.5 percent. Alloys, such as Hastelloy C, an alloy with the following percentage composition: Mo, 14-19; Fe, 4-8; C, D04-0.15; Cr, 12-16;

W, 3-5.5; remainder nickel, is also useful. In order to produce a product of high purity and low contamination the grinding media should be chosen as to avoid the Wearing away of particles therefrom.

The charge of grinding media ranges from about 3 percent effective volume to about 60 percent effective volume. Naturally, the effective volume depends to a large extent upon the specific gravity of the grinding media. The heavier the media the smaller the volume required. The effective volume is defined as follows: The grinding media to Kbe charged which fills a 1 cubic foot box by random packing is weighed. It is essential that the grinding lmedia be allowed to distribute itself randomly through the box without any orderly packing. The effective volume then is calculated by dividing the weight of the grinding media charged by the weight of 1 cubic foot of randomly packed grinding media and multiplying the same by the reciprocated volume of the drum 18 of the desublirnation apparatus. The resultant fraction multiplied by 100 yields the preferred effective volume.

The drum rotation is measured in revolutions per minute. The capacity of the apparatus is measured in pounds per hour and depends upon the drum speed, the density of the grinding media, the weight of the grinding media charged, the interior volume of the drum the roughness of the interior lining 29 of the drum. The critical speed of the cylindrical drum 18 may be measured by dividing 76.6 by the square root of the diameter of the drum in feet. It has been found that when the drum is rotated at from 3() to about 95 percent of the so calculated critical speed, good results are obtained.

The shape of the drum of the apparatus is important, and if the drum of the apparatus is cylindrical in shape the length of the cylinder should be 0.5 to 5 times the diameter of the cylinder.

The liner 29 of the drum of FIG. 6 is very important for obtaining a product with as little contamination as possible. In general a rather hard metal or alloy is very useful. Nickel is a preferred material for lining the drum. Other useful materials are carbon steel, titanium, Ni-hard blocks, Hastelloy C (see above) and Monel metal. In addition, the lining material is advantageously resistant to corrosion by the material to be desublimated. For example, nickel, the preferred lining, has excellent corrosion resistance to cyanuric chloride.

The following examples illustrate the invention but are not intended to limit the same thereto. In the examples, unless otherwise noted, parts are by weight and temperature in degrees centigrade. The relationship of parts Iby weight to parts by volume is that of pounds to cubic feet.

EXAMPLE 1 Cyanuric chloride vapor at the rate of 9 parts per hour is passed into the desublirnation apparatus illustrated in FIGS. 1-5 of the drawing, as modified in FIG. 6 with liner 29 being of nickel. The water-cooled drum 18 is rotated `at 45` revolutions per minute. The cyanuric chloride vapor is under approximately normal atmospheric pressure within the dr-um and enters the drum at an initial temperature of 200. The drum is charged with 20 parts of 1%@ inch by 1%; inch Burundum shapes. The cyanuric chloride desumblimated from the vapors within the drum and are removed by the shapes as the drum rotates. This solid cyanuric chloride passes out of the drum through the screen 20 at the end of the drum opposite to the end into which the vapors were introduced. The Burundum shapes are retained in the drum lby this screen.

The cyanuric chloride solid so obtained is in a finely divided state, at least 50% of which is less than 10 micron in particle size and `all of which is less than 40 micron in particle size. There are only parts of nickel per million parts of cyanuric chloride.

8 EXAMPLE 2 If in Example 1 the 1?/16 inch by 15716 inch Burundum shapes are replaced by 25 parts of 1% inch by 11A inch Burundum shapes, then cyanuric chloride is obtained in a nely divided state having only 160 parts of nickel per million parts of cyanuric chloride.

EXAMPLE 3 Cyanuric chloride vapor at the rate of 9 parts per hour is passed into the desublirnation apparatus (illustrated in the drawing, FIGS. 1-5) in which the drum rotates at 45 revolutions per minute. The cyanuric chloride within the drum is under approximately normal atmospheric pressure and enters the drum at a temperature of 200. The apparatus has an unlined drum of carbon steeel having a 12 inch diameter and 281A inch length with 4 horizontal lifting bars 53. The drum is water cooled. The drum is charged with 40 parts of steel balls each having a diameter of 1 inch. The steel balls are retained in the drum by means of the screen 20 at one end, through which the solid, nely divided cyanuric chloride passes after solidifying on the interior of the rotating drum. The products contains only 250 parts of iron per million parts of cyanuric chloride.

EXAMPLE 4 If in Example 3, the steel balls are replaced by parts of l inch Ni-hard balls and the feed rate of cyanuric chloride is changed from 9 parts per hour to 8 parts per hour, the cyanuric chloride solid is obtained in a finely divided state and contains only 400 parts of iron per million parts of cyanuric chloride.

EXAMPLE 5 If in Example 3 the inside of the drum is lined with a layer of 3%; inch thick Ni-hard blocks and steel balls are replaced by 90 parts of 11A inch `diameter Ni-hard balls and the cyanuric chloride vapor is introduced at the rate of 4 parts per hour, then cyanuric chloride solid is obtained in a finely divided state and contains 275 parts of nickel per million parts of cyanuric chloride.

EXAMPLE 6 If in Example 3, the interior of the drum s rst polished with sand and 1 inch Ni-hard balls and the cyanuric chloride is fed into the apparatus at the rate of 5 parts per hour, then cyanuric chloride solid is obtained in nely divided state and contains 260 parts of iron per million parts of cyanuric chloride.

EXAMPLE 7 A 6 inch length 6 inch diameter Pyrex pipe was rotated at 60 r.p.m. and cooled by blowing air on the outside. Inside the pipe there were 1424 g. of 13/16 x 1?/16 inch Burundum shapes and three 1A inch diameter steel bars coated with polyethylene tube fastened inch from the side of the walls. The hot aluminum chloride vapor was fed to one end of the pipe and a screen at the other end allowed powder to come through while retaining the Burundum shapes. With this apparatus anhydrous aluminum chloride was produced at a rate of 30 g./hr.

The product was a nely divided powder. The actual particle size is difficult to measure as the product rapidly picks up moisture from the atmosphere.

EXAMPLE 8 An apparatus similar to that used in Example 7, but in which the Burundum shapes were replaced by 2120 grams of M; inch steel cubes, and used, and naphthalene vapor was introduced into one end of the pipe. Finely divided naphthalene was produced at the rate of 50 g./hr., and having the following particle sizes:

Naphthalene- 70% below 20 micron 20% 20 to 50 micron 10% above 50 micron.

What is claimed is:

1. An apparatus for desublimating cyanuric chloride and the like, comprising a rotatable cooled initial desublimation chamber and a cooled nal desublimination chamber into which said initial desublimation chamber opens and having a cross-sectional area transversely or' the axis of the initial desublimation chamber which is at least as large as that of the initial desublimation chamber and the opening between the chambers being the entire cross-sectional area of the initial desublimation chamber, said initial desublimination chamber having an inlet at one end thereof, a liner of corrosion resistant material on the inside of said initial desublimation chamber, a screen across said opening between said initial desublimation chamber and said nal ldesublimation chamber, a charge of particulate tumbling grinding media in said initial desublimation chamber, said iinal desublimation chamber having an outlet therefrom for desublimated material and a vent for the escape of gases therefrom, the final desublimation chamber having a size for dissipating heat suiciently rapidly to desublimate cyanuric chloride in nely divided form directly from a mixture of gases therein, a collecting means depending from said outlet, and a cooling medium supply system positioned adjacent at least said rotatable initial desublimation chamber for flowing a cooling medium over the outside of said initial' desublimation chamber, whereby when desublimable vapor is supplied to said initial desublimation chamber and it desublimes, the desublimed material is simultaneously cleaned from the walls of the chamber and from the particulate tumbling grinding media and is cornminuted and ows through said screen as soon as it is comminuted to the size of the screen openings and cyanuric chloride remaining in the mixtuer of gases flowing into the final desublimation chamber is desublimated in iinely divided form in the mixture of gases.

2. An apparatus as claimed in claim 1 in which said nal desublimation chamber comprises an ambient air cooled hood around the end of said initial desublirnation chamber.

3. An apparatus as claimed in claim 1 in which said rotatable initial desublimation chamber is a rotatable drum, and a plurality of agitating rods mounted within said drum and spaced inwardly from said liner a distance of from 1/10 to 3%, the diameter of said drum.

References Cited UNITED STATES PATENTS 1,675,345 7/1928 Hall 23--264 2,316,043 4/1943 Billings et al. 23-313 3,015,451 l/l962 Goeser 241-176 2,021,671 ll/l935 Skinner 23-286 XR JAMES H. TAYMAN, JR., Primary Examiner U.S. Cl. X.R. 

